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14 | pmbaty | 1 | //=- CachePruning.h - Helper to manage the pruning of a cache dir -*- C++ -*-=// |
2 | // |
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3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
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4 | // See https://llvm.org/LICENSE.txt for license information. |
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5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
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6 | // |
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7 | //===----------------------------------------------------------------------===// |
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8 | // |
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9 | // This file implements pruning of a directory intended for cache storage, using |
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10 | // various policies. |
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11 | // |
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12 | //===----------------------------------------------------------------------===// |
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13 | |||
14 | #ifndef LLVM_SUPPORT_CACHEPRUNING_H |
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15 | #define LLVM_SUPPORT_CACHEPRUNING_H |
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16 | |||
17 | #include "llvm/Support/MemoryBuffer.h" |
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18 | #include <chrono> |
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19 | #include <optional> |
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20 | |||
21 | namespace llvm { |
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22 | |||
23 | template <typename T> class Expected; |
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24 | class StringRef; |
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25 | |||
26 | /// Policy for the pruneCache() function. A default constructed |
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27 | /// CachePruningPolicy provides a reasonable default policy. |
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28 | struct CachePruningPolicy { |
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29 | /// The pruning interval. This is intended to be used to avoid scanning the |
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30 | /// directory too often. It does not impact the decision of which file to |
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31 | /// prune. A value of 0 forces the scan to occur. A value of None disables |
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32 | /// pruning. |
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33 | std::optional<std::chrono::seconds> Interval = std::chrono::seconds(1200); |
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34 | |||
35 | /// The expiration for a file. When a file hasn't been accessed for Expiration |
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36 | /// seconds, it is removed from the cache. A value of 0 disables the |
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37 | /// expiration-based pruning. |
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38 | std::chrono::seconds Expiration = std::chrono::hours(7 * 24); // 1w |
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39 | |||
40 | /// The maximum size for the cache directory, in terms of percentage of the |
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41 | /// available space on the disk. Set to 100 to indicate no limit, 50 to |
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42 | /// indicate that the cache size will not be left over half the available disk |
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43 | /// space. A value over 100 will be reduced to 100. A value of 0 disables the |
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44 | /// percentage size-based pruning. |
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45 | unsigned MaxSizePercentageOfAvailableSpace = 75; |
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46 | |||
47 | /// The maximum size for the cache directory in bytes. A value over the amount |
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48 | /// of available space on the disk will be reduced to the amount of available |
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49 | /// space. A value of 0 disables the absolute size-based pruning. |
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50 | uint64_t MaxSizeBytes = 0; |
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51 | |||
52 | /// The maximum number of files in the cache directory. A value of 0 disables |
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53 | /// the number of files based pruning. |
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54 | /// |
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55 | /// This defaults to 1000000 because with that many files there are |
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56 | /// diminishing returns on the effectiveness of the cache. Some systems have a |
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57 | /// limit on total number of files, and some also limit the number of files |
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58 | /// per directory, such as Linux ext4, with the default setting (block size is |
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59 | /// 4096 and large_dir disabled), there is a per-directory entry limit of |
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60 | /// 508*510*floor(4096/(40+8))~=20M for average filename length of 40. |
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61 | uint64_t MaxSizeFiles = 1000000; |
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62 | }; |
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63 | |||
64 | /// Parse the given string as a cache pruning policy. Defaults are taken from a |
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65 | /// default constructed CachePruningPolicy object. |
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66 | /// For example: "prune_interval=30s:prune_after=24h:cache_size=50%" |
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67 | /// which means a pruning interval of 30 seconds, expiration time of 24 hours |
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68 | /// and maximum cache size of 50% of available disk space. |
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69 | Expected<CachePruningPolicy> parseCachePruningPolicy(StringRef PolicyStr); |
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70 | |||
71 | /// Peform pruning using the supplied policy, returns true if pruning |
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72 | /// occurred, i.e. if Policy.Interval was expired. |
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73 | /// |
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74 | /// Check whether cache pruning happens using the supplied policy, adds a |
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75 | /// ThinLTO warning if cache_size_bytes or cache_size_files is too small for the |
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76 | /// current link job. The warning recommends the user to consider adjusting |
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77 | /// --thinlto-cache-policy. |
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78 | /// |
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79 | /// As a safeguard against data loss if the user specifies the wrong directory |
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80 | /// as their cache directory, this function will ignore files not matching the |
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81 | /// pattern "llvmcache-*". |
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82 | bool pruneCache(StringRef Path, CachePruningPolicy Policy, |
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83 | const std::vector<std::unique_ptr<MemoryBuffer>> &Files = {}); |
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84 | } // namespace llvm |
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85 | |||
86 | #endif |